1. Field of the Invention
The invention relates to an improved apparatus for effecting the closing of an open seed furrow produced in soil by a tractor drawn planter which sequentially deposits seed into the open furrow as it is produced by the forward movement of the planter, and particularly to an apparatus capable of reliable closing of seed furrows produced in soil which has not received any cultivation subsequent to the harvesting of the previous crop.
2. Summary of the Prior Art
One of man's earliest occupations was the planting of seeds in the soil. With the advent of horse drawn tools, the 19th century saw the development of horse pulled planting units which incorporated a furrow opening device, a seed depositing mechanism operated manually or by ground engaging wheels to sequentially deposit seed in the open furrow, and followed by an apparatus for moving soil into the open furrow to cover the seed. See for example, U.S. Pat. Nos. 22,676 to Seaman and 489,037 to Roadhouse.
In each of these very early patents, the filling of the open top furrow was accomplished by a pair of disc-shaped wheels having a plurality of relatively short radial projections spaced around the peripheries of the disc-shaped wheels. Such projections were pointed and entered the ground a limited distance to rotate the wheels by the forward movement of the horse pulled planter, but also to throw dirt particles upwardly and rearwardly into the open furrow. For these prior art devices to be successful, the soil bed had to be well prepared in advance of planting. Leftover stubble and stalks from the previous crop would, when encountered by the disc-shaped wheels, raise such wheels and defeat the dirt throwing action, thus leaving a portion of the furrow uncovered and preventing the germination of the seeds in such portion.
In the intervening years, many other furrow closing apparatuses have been tried, such as scrapers or curved discs disposed on opposite sides of the open furrow and operating to laterally displace two bands of soil and move same into the seed furrow. (See FIGS. 1a and 1b for a schematic showing of such prior art furrow closing apparatus.) Again, these mechanisms functioned well in well prepared soil beds, but if stubble or trash was on the field, or the soil comprised a large percentage of clay, the furrow closing operation was less than desirable. Trash or stubble would effect an undesired elevation of the furrow closing apparatus. When operating in clay soils, not only would the furrow wall be compacted by its formation, but the two clay strips cut by the discs would be compacted together to form an unpenetrable barrier above the germinating seed.
In recent years a new approach to farming in arid areas of the country has been successfully introduced. Instead of plowing the field to bury the stubble and trash from the previous crop, the new approach is to plant the field without soil preparation, hence with the stubble and trash from the previous crop on the surface. The presence of such trash on the surface substantially diminished the loss of water from the soil and, where irrigation is employed, substantially reduced the amount and frequency of water application.
A popular planter utilized in such areas is Model No. 7100, manufactured and sold by John Deere Co. of Moline, Ill. This planter provides a rearwardly projecting subframe pivotally mounted to the planter frame for movements in a vertical plane. An adjustable tension spring urges the subframe toward the ground. A pair of discs called coulters are rotatably mounted on the subframe and are gravity and spring biased into respective engagement with opposite sides of the seed trench or furrow. The coulters are provided with notches in the sharpened periphery of the discs and such notches are supposed to facilitate the cutting of trash by the coulters. See U.S. Pat. No. 2,924,189 to Macleod.
Despite the provision of notches in the cutting periphery of the coulters, it has been observed that corn stubble will still cause undesired elevation of the coulters, hence leaving open spots in the seed furrow. More importantly, when used in clay soils, the coulters produce a compacting of the two strips cut along the sidewalls of the furrow to form a solid barrier to plant growth from the deposited seeds in the covered furrow.
In light soils, such coulters move too much soil forming a ridge over the deposited seed.
From the foregoing discussion, it is readily apparent that an improved covering apparatus for seed furrows is highly desired by a major segment of the crop farming industry.